Group audiphone system



Oct. 5, 1937.. s. G. sEARs GROUP AUDIPHONE SYSTEM FiledDc-t. 11, 1955 2Sheets- Sheet 1 lNvsN-ro 1 AT NEY Oct. 5, 1937. s. e. SEARS 2,094,681v

GROUP AUDIPHONE SYSTEM v Filed Oct. 11, 1935 2 Sheets-Sheet 2 IINVENTORW RN J CZ Patented Oct. 5, 1937.

UNITED STATES PATENT OFFICE GROUP AUDIPHONE SYSTEM Application October11, 1935, Serial No. 44,515

6 Claims.

This invention relates to a group audiphone system and has particularreference to a plurality of individual hearing aid devices responsive toa common remote sound transmitting source and especially adapted foraiding the hard-ofhearing among the audience of a theater, thecongregation of a church, the assembly of a convention, or any othergathering or groups of persons to clearly hear the entertainment,services, or

0 proceedings, with comfort and convenience.

Inasmuch as it is obviously impracticable to provide a hearing aiddevice for each seat in a theater, church, or the like, and isimpossible to properly distribute a number of such devices to therelatively few deaf persons for actuation from a commonsource of sound;such as the speaker's or actors microphone, the sound reproducingapparatus of a talking picture machine, or the like, the arrangementheretofore has been to provide each seat with a connection box withwhich a portable hearing aid receiver may be connected by the individualuser, the connection boxes being connected in series or parallel withthe transmitting microphone and amplifier, talking picture machine, orother source of sound in which the bearer is interested. jHowever',because these individual receivers are usually not connected in thetransmission circuit at the same time, the intermittent connection anddisconnection of the several receivers by the users creates an almostcontinually varying load on' the system during certain periods, with theresult that the reception of the sound by the several users varies,causing frequent adjustment of their individual volumecontrol rheostatswith consequent diversion of attention, nuisance and discomfort.

In accordance with the present invention, a group audiphone system isprovided, which may be either temporarily or permanently installed in atheater, church or other auditorium or gathering place with ease andrapidity, which is so arranged that the distribution of the individualreceivers may be varied at will according to the number and location ofthe persons requiring them, which is adjustable in accordance with thedistance of the source of sound from the microphone and requires nofurther adjustment, and with which the transmission of the sound remainsuniform, clear and undisturbed, no matter how connected into or out ofthe circuit during the period of transmission of the sounds.

More particularly, the invention comprises an amplifier provided with avolume control variably calibrated to the distanceof the source of soundmany of the individual or groups of receivers are from the microphoneand having a resistance or impedance connected across its outputterminals, which is substantially equal to the resistance or impedanceof the maximum number of individual receivers, and which is disconnectedwhen the 5 load, which is substantially equal to the maximum number ofindividual receivers, is connected thereto.

This substitute load is represented by complementary resistances orimpedances preferably connected in series and located in junction orjack boxes connected by a main cable for distribution at properlylocated central points throughout the auditorium, the number of suchresistances or impedances equalling the number of sub-distributingconnections required, .and aggregating a resistance or impedancesubstantially equal to the substitute load resistance or impedance inthe amplifier and consequently substantially equal to the load of themaximum number of individual receivers.

Each of these sub-distributing connection box resistances or impedancesis substantially equal to the total resistance or impedance of thecorresponding bank of individual receivers allotted to that junction boxand is disconnected when this bank is connected to the box. Therearecorresponding jack boxes for receivers, and each of them is providedwith a resistance or impedance substantially equal to the resistance ofthe corresponding receiver and disconnected when that receiver isplugged in.

These substitute resistances or impedances for the receivers arepreferably connected in parallel, so that the entire distribution systemis connected in series-parallel, and the several substitute loads forthe indlvidual'receivers, each group or bank of receivers and of theentire distribution system are complementary and correlated in such away that the amplifier is serving a full load at all times, regardlessof the number of receivers in service at any one time and the volume andquality of the sound are unaffected and the reception is undisturbed byclicks or contact noises due to connection or disconnection of one ormore receivers in the system during the period of the soundtransmission. This series-parallel arrangement also protects the systemand apparatus against injury as the result of short-circuiting of ajack, for example by an extraneous conductor inserted therein, ashort-circuited receiver cord, or sub-distribution cable, or the like.Also, broken or otherwise open receiver cords or the like, are preventedfrom afiecting the system in a detrimental way. 55

The receiver jack boxes for temporary or portable installations comprisehousings provided with a clamp or hook whereby they may be supported onor by the rear of the chair or seat in front of the user and areconnected to the redistributing cable. Each of these portable jack boxescontains the substitute load resistance for the corresponding individualreceiver, and is fitted with a jack for receiving the plug of thereceiver, which is suspended from a hook on the jack box when not inuse. A.flat plug having little lateral projection is provided and thecord connecting the receiver thereto is preferably fitted with a volumecontrol rheostat. For permanent installations such as for theaters, inwhich the amplifier is connected directly to the sound-reproducingapparatus of the talking picture machine, the receiver jack boxes arepreferably secured to the underside of every other arm and are providedwith double jacks, one for each adjoining seat.

It will be seen that with the group audiphone arrangement of thisinvention, a very simple, fool-proof and efiective system of sounddistribution for the hard-of-hearing is provided, which may be readilyinstalled and operated with a minimum of labor and with a maximum ofeffectiveness and satisfaction to the users. Further advantages ofthe-invention will become ap-. parent upon examination of theaccompanying drawings, in which:

Figure 1 illustrates the manner in which the group audiphone system ofthis invention may be installed; 7

Fig. 2 is a distribution wiring diagram of the same;

Fig. 3 is an enlarged perspective view of one o the portable jack boxes;

Fig. 4 is a distribution wiring diagram for a theater; and

Fig. 5 is an enlarged view of the amplifier range adjustment dial.

Referring to Fig. l of these drawings, numeral Ill designates amicrophone located on a stage or rostrum I l or the like and connectedby a cable I l to an amplifier l2, which is energized from a suitablesource of power connected thereto by cable 13 and which is provided witha jack adapted to receive the plug N connected to the main distributioncable l5. In a temporary. installation this distribution cable is laidalong the floor, such as along the aisle of the theater or the like, andis provided at spaced intervalswith jack boxes IS, the number of whichdepends upon requirements, such as the number of tiers-of seats orchairs to be served.

Jack boxes l6 preferably have two jacks to p which are connectible bysuitable plugs I! the subdistribution cables l8 leading-to a pluralityof individual jackboxes l9 preferably supported on the seats or chairsimmediately in front of the position where the hea ers sit, as isindicated in Fig. 3. These individual jack boxes H) are each providedwith a spring hook or clamp 20' adapted to support the box on the backof the chair, and a hook 2! or the like on its underside upon which theheadband 22 of the audiphone receiver 23- may be conveniently suspendedwhen the re-" ceiver is not in use.

The audiphone receiver 23 may be of the conventional air conduction typeor may be of the bone conduction type, as is illustrated, and adapted tobe held against the bone structure of the user, such as on the mastoideminence behind the ear, by means of the headband 22, The electric cord24 leading from the receiver 23 is fitted with a volume control rheostat25 and with a fiat plug 26,adapted to be inserted in the jack box l9.The head of the plug 26 is made fiat, as

The arrangement illustrated is convenient and satisfactory for atemporary installation but if a permanent installation is required thecables I5 and I8 may be laid in conduits in thefloor or the like, theamplifier l3 concealed and the microphone l located at suitable points,such as at Hi. 1

As is illustrated in the wiring diagram of Fig. 2, the output terminals21 of the amplifier l3 are bridged by a resistance 28, which issubstantially equal to the predetermined full load of the groupaudiphone system, so that, whether or not the plug I l of the maindistribution cable I is plugged into the jack 29, the load on theamplifier I2 is constant. The contact spring 30 of the jack 29 whenengaged by'the tip 3| of the plug I4 is moved out of engagement with thecontact 32, to which one end of the resistance 28 is connected, so thatthe latter is disconnected from the output circuit of the amplifier l2.Simultaneously, the engagement of the tip and sleeve of the plug withthe contact spring and sleeve of jack 29 connects the main distributioncable I 5 into the amplifier output circuit. Withdrawal of the plug I6releases contact spring 30 so that it reengages contact 32 andreconnects resistance 28 across the output terminals 21 of the amplifieri2.

By way of illustration, if the plan of the auditorium requires as manyas ten subdistribution cables I8 in order to secure proper distributionof the individual audiphone receivers 23, ten resistances 32 arepreferably connected in series in the main distribution cable l5, eachof these resistances being substantially equal to the full load of thecorresponding subdistribution cable I 8 and all of them aggregating atotal resistance which is substantially equal to the resistance ofresistance 28 in the amplifier. For example, if the total predeterminedload on the amplifier is 100 ohms the resistance of each individualresistance 32 is ten ohms.

In the arrangement illustrated in Figs. 1 and 2, two of such resistancesare placed in each subcontacts 35, disconnecting the resistance 32.

Contact spring 34 is connected to the correspond- -ing wire of maindistribution cable I 5 on one side of resistance 32 and the sleeve ofthe jack 33 is connected to the opposite side of the resistance 32, sothat the insertion of plug I'I efiects connection of the subdistributioncable I 8- to the main distribution cable l5.

The plurality of individual jack boxes I 9 of subdistribution cable I8"each contain the jack 31 and a resistance 38, which is substantiallyequal to the resistance of the audiphone receiver 23. The resistances 38are connected in parallel in subdi'stribution cable l8 and are soarranged that their net resistance is substantially equal to theresistance of resistance 32; For example, if the resistance of audiphonereceiver 23 is 50 ohms and there are five individual jack boxes I!) foreach subdistribution cable l8, the resistance 38 in each of them issubstantially equal to 50 ohms, and since there are five individual jackboxes IS, the net resistance of the five resistances 38 is 10 ohms,according to the reciprocal rule regarding parallel resistances.

Each individual resistance 38 is preferably connected at one end to oneof the wires of the subdistribution cable I 8 and at the other end tocontacts 39 normally closed by contact spring 48 of the jack 31, whichis connected to the other wire of the subdistribution cable l8. When theplug 28 of the audiphone receiver 23 is plugged into jack 3! the tip ofthe plug causes contact spring 48 to disengage contact 33, therebydisconnecting resistance 38.

In operation, each of the elements of the group audiphone system of thisinvention is represented by a substitute load, so that the system isunder full load at all times, no matter how few or how many of theindividual audiphone receivers 23 are in use and no matter how few orhow many of the subdistribution cables 18 are in use. Thus, the maindistribution cable i may be laid and, as each of the subdistributioncables is connected by its plug I! to the corre-' sponding 'jack boxill, the resistance 32 corresponding to thesubdistribution cable, isdisconnected and substituted by the net resistance of the individual. -resistances 38, which is substantially equal to resistance 32. Similarly,as each of the individual audiphone receivers 23 is plugged into a jackbox IS; the resistance thereof is substituted for the resistance 38,which is disconnected but which is reconnected and becomes a substituteload for the audiphone receiver 23 when the latter is disconnected.

With this arrangement, there is no fluctuation in the load on theamplifier of the group audiphone system and none of the individual usersis disturbed by clicks or a change in reception by the connection anddisconnection of individual audiphones during the period of the soundtransmission, so that transmission remains clear and uniform under alloperating conditions Also the present arrangement provides a veryflexible and simple system which may be installed in many different waysto suit circumstances and requirements.

For permanent installations, and especially those in theaters or thelike, where the amplifier I2 is directly connected to the soundreproducing apparatus of talking picture machine, or the like, theindividual jack box installations may be more or less permanent andattached to the under side of every other arm of the seats. To that endthe arrangement illustrated in Fig. 4 is utilized in which the jackboxes 39 are suitably secured to the under side of the seat arms and areprovided with opposite jacks, one for each adjacent seat. The substituteload resistances 4| for the two corresponding audiphone receivers 23 areconnected in series in the series-parallel arrangement of thesubdistribution cable i8.

The sleeve of the jack 48 is connected by a wire 42 to one end of thecorresponding resistance 4|, and the contact spring 43 of the jack 40'normally closes contacts 44 connected to the other end of the resistancewhen the plug 26 of the audiphone receiver 23' is inserted in jack 48',its tip causes contact spring 43 to disengage contacts 44, disconnectingresistance M from the circuit. Conversely, when plug 23' is withdrawn,contact 43 is released to close contacts 44 to reintroduce substituteload resistances 4| into the distribution circuit. As shown in Figs. 3and 4 the audiphone receivers 23 and 23' may be held by headbands 22, orby the handle 45, and a volume control rheostat '25 of the button typemay be used or one of the slider type, such as indicated at 46 in Fig.4, may be used.

The location of the source of sound from the microphone ill or illnormally determines the degree of amplification necessary for theaudiphone system. Accordingly, the rheostat'of the amplifier of thisinvention is calibrated to the distance of the source of soundfrom themicro! phone. For example, if the distance X of the speaker is ten feetfrom the microphone ill in Fig.= 1, rheostat 41 is adjusted so that itspointer -48 indicates III on the dial 49, which is subdivided into feetof microphone range, as is indicated in Fig. 5. This adjustment remainsconstant for all transmission purposes and need be varied only when thedistance of the source of sound of the microphone l0 varies materially.

While several preferred embodiments of the invention have beenillustrated and described herein, it is to be understood that theinvention is not limited thereby, but is susceptible of changes in formand detail within its scope. The term resistance as used herein and inthe appended claims is regarded for purposes of this application assynonymous with or comprehending an impedance.

I claim:

1. In a group audiphone system, the combination of a source of soundtransmission, a main distribution line connected thereto and having aplurality of spaced resistances connected in series and having a totalresistance substantially equal to the predetermined full load of thesystem, a plurality of subdistribution lines adapted to be connectedindividually across each of, said resistances for disconnecting them, aplurality of spaced resistances connected in parallel in eachsubdistribution line and having a total resistance substantially equalto the corresponding resistance in the distributing line, and aplurality of audiphones each adapted to be connected across asubdistribution line resistance for disconnecting it and having aresistance substantially equal to said subdistribution line resistance,whereby the load on the source of sound transmission remains constantregardless of the connection and disconnection of the severalsubdistribution lines and audiphones in the main distribution line.

2. In a group audiphone system, the combination of a source of soundtransmission, an amplifier therefor, a resistance across the outputterminals of the amplifier and. substantially equal to the predeterminedfull load of the system, a distribution line ccnnectible across theoutput terminals of the amplifier for disconnecting the said resistance,a plurality of resistances in said distribution line substantially equalin total resistance to the said predetermined full load of the system,-said resistances being connected in series, a plurality ofsubdistribution lines adapted to be connected individually across eachof said resistances for disconnecting them, a plurality of spacedresistances connected in parallel in each subdistribution line andhaving a total resistance substantially equal to-the correspondingresistance in the distributing line, and a plurality of audiphones eachadapted to be connected across a subdistribution line resistance fordisconnecting it and having a resistance substantially equal to saidsubdistribution line resistance, whereby the load on the source of soundtransmission remains constant regardless of the connection anddisconnection of the several subdistribution lines and audiphones in themain distribution line.

3. In a group audiphone system, the combination of a source of soundtransmission, an amplifier connected thereto, a plurality of spaced jackboxes, a distribution cable connecting said boxes to the amplifier, aplurality of subdistribution cables, a plug for each of saidsubdistribution cables for connecting the latter to corresponding jackboxes, spaced jack boxes in each subdistribution cable, an amplifier foreach subdistribution jack box having a plug for connection with thelatter, a resistance in each subdistribution cable jack boxsubstantially equal to the resistance of the corresponding audiphone andadapted to be disconnected by the plug of the latter, a resistance ineach distribution cable jack box substantially equal to the totalresistance of the subdistribution cable and adapted to be disconnectedby the plug of the latter, whereby the load on the system remainsconstant regardless of the connection and disconnection of theaudiphones and subdistribution cables in or out of the system.

4. In a group audiphone system for theaters and the like, thecombination of a source of sound, a remote jack box supported onalternate seats of a row, double jacks on the jack box connected inseries to the source of sound, a resistance connected across thecontacts of each jack, and a normally-closed switch between one side ofthe resistance and one of the jack contacts adapted to be opened by aplug inserted in the jack.

5. In a groupaudiphone system, the combination of a microphone, anamplifier connected thereto, a rheostat in the amplifier circuit forcontrolling the output volume thereof, a dial for the rheostat dividedin increments of distance of the source of sound from the microphone,and a plurality of audiphones connected to the amplifier.

6. In a sound transmission system, the combination of a transmitter, anelectrical sound amplifier connected thereto, a receiver connected tothe amplifier, an adjustable volume control for the amplifier, a pointerthereon, and a dial for the pointer divided in increments of distance ofthe transmitter from the source of the sound to be transmitted.

STERLING G. SEARS.

